Overheated I think I hurt it

[big dreamer racing]

1977 140hp johnson
Was out Sunday drove around a bit like 1/2 hour all OK then shut it down to get the tube ready, after finally getting the engine to run (other issues) we take off toward the beach to picnick instead, the engine had barely any power @ WOT and I notice a burning paint like smell 1/2 way along the trip
(5 minutes)
look over and see excessive smoke from the top of the engine shut it down beached it and noticed the port side head is black & smoking, and the sensor was melted.
The starboard side looks ok wasn't abnormally hot to touch.

Please help I haven't taken anything apart yet but I believe the port side
t-stat stuck shut or got plugged up, we were stuck in some sand during start up. I hope nothing got damaged, (aka expensive parts) hopefully new t-stats & a water pump repair. I'm again about to give up & go back to building my camaro instead. Also last week we named the boat "money 4 nothing" I guess that name fits now.

 

[Barnacle_Bill]

Re: Overheated I think I hurt it

You need to do a compression check. Let us know the readings.

 

[R.Johnson]

Re: Overheated I think I hurt it

Don't even fool with a compression test. Remove the cylinder head, and intake bypass cover's. Check the cylinder walls. and piston rings, and skirt. Somebody is going to come back with a different idea, such as, " if we don't see it, or talk about it, it will go away" That bank of cylinders got very hot.

 

[big dreamer racing]

Re: Overheated I think I hurt it

Well then I guess I get to take another engine apart, I hope it didn't damage anything, but with my luck with this engine it's fubar.

 

[ezeke]

Re: Overheated I think I hurt it

As R.Johnson said, it is just taking off the cylinder head and the bypass cover for inspection. You will want to replace that #4 ignition coil, the head gasket bypass gasket and the water deflectors, so pick those up before you start.

The sand may have stuck in the thermostat housing or in the waterpump. If you had the water intake screens in place, the sand will be very small granules and should wash out easily.

If you loosen the hoses at the bottom of the cylinder heads that lead to the thermostat housing, you can see if the sand made it that far and partially flush the system from there.

 

[F_R]

Re: Overheated I think I hurt it

Actually, the intake bypass covers are on the cool side of the pistons. If you want to see the damage you did, remove the exhaust covers (the bubbleback in the center). That is where you will see the scuffed piston skirts.

 

[kenmyfam]

Re: Overheated I think I hurt it

Looks like she warmed up pretty good.
Agree with the other posters about taking apart to have a look to begin with.
Anything that looks like that is generally not good news !!!!

 

[ottertail]

Re: Overheated I think I hurt it

Not to be one to disagree here but do the compression test or beter yet a cylinder leak down test before pulling it apart. It would not be the first time a set of rings went soft from the overheat and not totally scored the cylinder. After the test, then take it apart. There is no doubt that there will be damage on an overheat this severe. I would hate to have you pull it down and see no scoring and reassemble it and have it not run on that bank and have to start over.

 

[kenmyfam]

Re: Overheated I think I hurt it

Not to be one to disagree here but do the compression test or beter yet a cylinder leak down test before pulling it apart. It would not be the first time a set of rings went soft from the overheat and not totally scored the cylinder. After the test, then take it apart. There is no doubt that there will be damage on an overheat this severe. I would hate to have you pull it down and see no scoring and reassemble it and have it not run on that bank and have to start over.

I would be replacing rings at least no matter what after something that severe !!!!

 

[big dreamer racing]

Re: Overheated I think I hurt it

Okay I checked the rings & they "seem" okay, moving freely on the piston, no bad scrapes, good amount of oil in the cylinder. No other discoloration of the engine just on the top cylinder cover area. The t-stats were ugly looking as in needing replaced soon, and it melted the bypass valve. I guess I'll be pricing rings & gaskets.
Damn this engine is ticking me off, finally got it running fairly good, bam this happens. Oh well I'm either determind or stupid.

 

[jbjennings]

Re: Overheated I think I hurt it

Did you figure out what stopped water flow to the left bank? Better get it figured out bofore you put it all back together. good luck with it,
JBJ

 

[F_R]

Re: Overheated I think I hurt it

I guess that means you didn't pull the exhaust cover, huh? The issue here is not rings but piston skirts. If they are not scored, replace all the gaskets, fix the cooling problem and run it. But if they are scored, bad news.

 

[R.Johnson]

Re: Overheated I think I hurt it

FR is certainly right about that exhaust cover, I was just thinking you may find damage on either side with that much heat. That engine has the bubble back exhaust cover, it can be a real bear to remove with the power head in place.

 

[big dreamer racing]

Re: Overheated I think I hurt it

Yea, I removed the bubble and the exhaust plate, looked @ the pistons from the exhaust ports they look good, the rings move freely, no scrapes in the cylinders that I can see, also used a bore scope to look inside the cylinders.
The overheating cause was a clogged t-stat on the port side, I will flush out the engine when I have the chance.

 

[F_R]

Re: Overheated I think I hurt it

Then put it back together with new gaskets and see how it goes.